In prior systems, cache memory has been used to improve performance of central processing units (CPUs) in computer systems. This cache memory is typically small in size as compared to main memory and is used to hold a segment of main memory for use by the CPU in its operations. To the extent the CPU can use instructions in cache memory without having to pull new information from main memory, CPU performance is typically enhanced. For this reason, it is often desirable to increase the cache memory size. Limitations exist, however, that hinder the ability to add more physical memory. For example, many operating systems limit how much main memory and cache memory a system can physically access. To increase the effective size of CPU cache memory, therefore, prior solutions have proposed the use of cache compression within the cache memory.
With respect to database environments, a portion of the main memory for the computer system managing the database is often used by the database management application as a database cache for data being read from or written to the stored database file. The database cache provides a buffer between the access, create and modify instructions from the database users and the database file itself. In addition, the database cache can provide for improved access times to client systems to the extent that the database management application can satisfy queries to the database from the data currently sitting in the database cache. The database file is typically stored on some physical media, such as one or more hard disks. With respect to the storage of large database files, prior work has focused on using data compression algorithms to reduce the size of the database files stored on hard drives. In addition, because most existing database access protocols operate on uncompressed data, prior work has also focused on protocols and query methodology for directly accessing the compressed data where the database file is compressed on disk. However, with increases in the speed of CPUs outpacing the speed of disk access, this disk compression can provide only limited improvement due to the physical limitations related to accessing data from a physical disk.